Search results for "Note"
showing 10 items of 10709 documents
Modelling electric field control of the spin state in the mixed-valence polyoxometalate [GeV14O40]8−
2013
International audience; : The two-electron reduced mixed-valence polyoxometalate [GeV14O40](8-) presents an unusual paramagnetic behaviour as a consequence of the partial trapping of these electrons. The effect of applying an electric field is that of inducing antiferromagnetic coupling between the two delocalized electronic spins.
Latvijas Republikas Valsts prezidenta ievēlēšana un tā pilnveidošanas aspekti
2020
Jau vairākus gadus Latvijā gan iedzīvotāju vidū, gan parlamenta telpās ir izskanējis tāds variants, ka tauta varētu vēlēt Valsts prezidentu vispārīgās, vienlīdzīgās, tiešās un aizklātās vēlēšanās. Jāatzīst, ka šādas vēlēšanas nav raksturīgas valstīm ar parlamentārās republikas valsts iekārtu, kur Valsts prezidentu ievēlē pats parlaments, kurā konstitucionālos pienākumus pilda tautas vēlēti deputāti. Bet gan šāds regulējums ir izplatīts valstīs, kuras ir federācijas vai arī Valsts prezidentam ir plašākas pilnvaras nekā parlamentārās republikās. Galvenais šī darba mērķis bija aplūkot Valsts prezidenta ievēlēšanas procedūru Latvijas Republikā, kā arī salīdzināt to ar citām valstīm, no kurām ie…
Natural optical anisotropy of h-BN: Highest giant birefringence in a bulk crystal through the mid-infrared to ultraviolet range
2018
The giant birefringence of layered h-BN was demonstrated by analyzing the interference patterns in reflectance and transmittance measurements in the mid-infrared to the deep ultraviolet energy range. The refractive index for polarization perpendicular to the c axis is much higher than the refractive index for polarization parallel to the c axis, and it displays a strong increase in the ultraviolet range that is attributed to the huge excitonic effects arising from the unique electronic structure of h-BN. Thus, h-BN is shown to exhibit a giant negative birefringence that ranges from -0.7 in the visible to -2 in the deep ultraviolet close to the band gap. The electronic dielectric constants f…
Vanadium Carbide Dissolution during Austenitisation of a Model Microalloyed FeCV Steel
2005
High performance commercial micro alloyed steels contain elements such as vanadium, which leads to a fine dispersion of vanadium carbide precipitates. The precipitation state, in terms of volume fraction and size distribution, plays a significant role in final mechanical properties of the material. Different austenitisation heat treatments were performed on a model ternary alloy FeCV. Precipitation states were characterised combining different experimental techniques. TEM was used to identify the chemical composition of observed precipitates. ICP mass spectroscopy was performed to measure the volume fraction of precipitates. The size distribution was studied by SEM. Results are characterist…
Low-temperature molecular layer deposition using monifunctional aromatic precursors and ozone-based ring-opening reactions
2017
Molecular layer deposition (MLD) is an increasingly used deposition technique for producing thin coatings consisting of purely organic or hybrid inorganic-organic materials. When organic materials are prepared, low deposition temperatures are often required to avoid decomposition, thus causing problems with low vapor pressure precursors. Monofunctional compounds have higher vapor pressures than traditional bi- or trifunctional MLD precursors, but do not offer the required functional groups for continuing the MLD growth in subsequent deposition cycles. In this study, we have used high vapor pressure monofunctional aromatic precursors in combination with ozone-triggered ring-opening reactions…
Water Adsorption in Flexible Gallium-Based MIL-53 Metal–Organic Framework
2014
Understanding the adsorption of water in metal–organic frameworks (MOF), and particularly in soft porous crystals, is a crucial prerequisite before considering MOFs for industrial applications. We report here a joint experimental and theoretical study on the behavior of a gallium-based breathing MOF, Ga-MIL-53, upon water adsorption. By looking at the energetics and thermodynamics of Ga-MIL-53, we demonstrate why it behaves differently from its sibling Al-MIL-53, showing a different phase at room temperature (a nonporous phase) and the presence of a hydrated narrow-pore structure at gas saturation pressure. Moreover, we present a complete water vapor pressure vs temperature phase diagram of…
The impact of intercellular communication for the generation of complex multicellular prevascularized tissue equivalents
2019
In reconstructive surgery the use of prevascularized soft tissue equivalents is a promising approach for wound coverage of defects after tumor resection or trauma. However, in previous studies to generate soft tissue equivalents on collagen membranes, microcapillaries were restricted to superficial areas. In this study, to understand which factors were involved in the formation of these microcapillaries, the levels of the angiogenic factors vascular endothelial growth factor (VEGF), Interleukin-8 (IL-8), and basic fibroblast growth factor (bFGF) in the supernatants of the tissue equivalents were examined at various time points and conditions. Additionally, the influence of these factors on …
Vascular Endothelial Growth Factor-Releasing Microspheres Based on Poly(ε-Caprolactone-PEG-ε-Caprolactone)-b-Poly(L-Lactide) Multiblock Copolymers In…
2020
Pancreatic islet transplantation is a promising advanced therapy that has been used to treat patients suffering from diabetes type 1. Traditionally, pancreatic islets are infused via the portal vein, which is subsequently intended to engraft in the liver. Severe immunosuppressive treatments are necessary, however, to prevent rejection of the transplanted islets. Novel approaches therefore have focused on encapsulation of the islets in biomaterial implants which can protect the islets and offer an organ-like environment. Vascularization of the device’s surface is a prerequisite for the survival and proper func- tioning of transplanted pancreatic islets. We are pursuing a prevascularization s…
Veterināro preparātu atlieku noteikšana ar masspektrometrijas metodēm
2004
Analysis of veterinary drugs residues using masspectrometric methods. Bartkevičs V.. supervisors Dr.chem,J.Ģībietis. Dissertation. 65 pages, bibliography 55 citations. In Latvian. VETERINARY DRUGS. GAS CHROMATOGRAPHY. HIGH PERFORMANCE LIQUID CHROMATOGRAPHY, MASS SPECTROMETRY. LEVAMIZOLE, STEROID SUBSTANCES, ANTIBIOTICS, NSAID GROUP COMPOUNDS. This dissertation is dealing with determination of veterinary drug residues using masspectrometric methods. Survey of publications dealing with analysis of levamisole, nonsteroid anti-inflammatory drugs, steroid compounds and sulphonamides was performed. Masspectrometric methods for determination of residues of 33 different compounds are elaborated. Ma…
Analytical chemistry on many-center chiral compounds based on vibrational circular dichroism: Absolute configuration assignments and determination of…
2019
The absolute configuration of a chiral molecule is key to its biological activity. Being able to find out what this configuration is, is thus crucial for a wide range of applications. The difficulties associated with such a determination steeply rise as the number of chiral centers in a given compound becomes larger. Concurrently, it becomes increasingly more challenging to determine the levels and identity of potential stereochemical contaminants in a given sample with one and the same technique, leading in practice to extensive and laborious efforts employing multiple analytical techniques. Here, experimental and theoretical studies based on Vibrational Circular Dichroism (VCD) are presen…